Portobellos are mature crimini mushrooms primarily known for a brown, flat cap that takes on a meat-like flavor and texture when cooked. However, it's fine to use the stems of portobello mushrooms in cooking, according to Kathy Maister's Startcooking.com. After wiping the dirt off of portobello mushrooms with a soft brush or a moistened paper towel, cut out the stems, trim them and eat them in a variety of recipes, ranging from sautés to broth.

Duxelles

"Fine Cooking" recommends using portobello mushroom stems to prepare duxelles. Duxelles consists of minced onions, garlic and mushrooms cooked into a thick mixture in butter and seasoned with salt, pepper and herbs. Use duxelles to add a boost of flavor to sauces or soups, use several teaspoons as a meat or vegetable stuffing or bake inside pastry. You can freeze leftover duxelles in ice cube trays and store them in a zip-top plastic bag in the freezer for easy use whenever needed.

Mushroom Stuffing

"Christian Science Monitor" contributor Nora Dunne suggests using portobello mushroom stems as part of the stuffing when you're preparing vegetarian burger-style stuffed portobello mushroom caps. After cleaning the mushrooms and removing the stems, Dunne advises lightly sautéing the caps in olive oil, then filling each with a sautéed mixture of chopped portobello stems, minced garlic, diced onion and breadcrumbs. Top each stuffed mushroom with shredded cheese, bake until lightly browned and serve as a main dish or appetizer.

Mushroom Broth

Use portobello mushroom stems along with chopped white mushrooms and dried mushrooms like shiitake or porcini to make a rich mushroom broth, says "Food & Wine" chef Gordon Hamersley. Cook the fresh mushrooms and portobello stems with garlic and onions in vegetable oil, then add soy sauce, white wine, water and dried mushrooms along with seasonings. Simmer the mixture until it's reduced, strain it through a fine mesh sieve to remove all the solids, cool it and store it in the refrigerator. Use the broth as a substitute for water or stock in any recipe, such as risotto, soup or sauces.

Mushroom-Stem Omelet

If you have portobello mushroom stems left over after preparing a recipe that calls for only caps, "Gourmet" writer Ruth Cousineau says to try slicing them thinly, sautéing them with chopped shallots in butter and using them as a flavorful omelet filling. Cousineau recommends topping the mushroom-stem filling with grated Gruyere cheese. If you're concerned about your cholesterol and saturated fat intake, substitute extra-virgin olive oil for the butter and prepare the omelet with all or some of the egg yolks removed.